ISB Exam 1: Ch 3

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Chapter 3: Evolution, Biodiversity, and Population Ecology

What was discovered in Monteverde, Costa Rica in 1964?

Golden Toads

Species

A population or group of populations, whose members share common characteristics. They can breed with one another and produce fertile offspring

Population

A group of individuals of a species that live in the same area

Evolution

Means change over time

Biological Evolution

Genetic change in populations over time. Genetic change leads to changes in appearance, functioning or behavior over generations

Natural Selection

Traits that enhance survival and reproduction. These traits are past on more frequently to future generations that those traits that do not aid in survival and reproduction.

What must we understand in order to appreciate environmental science?

Natural Selection

What did Charles Darwin and Alfred Wallace propose in 1858?

They proposed natural selection as the mechanism of evolution

Adaptation

The process where, over time, characteristics that lead to better reproductive success will evolve in the population

Adaptive Trait

A trai that promotes reproductive success

Mutations

Accidental changes in DNA that may be passed on to future generations.

What also leads to genetic variation?

Sexual Reproduction

Natural Selection changes characteristics through:

-Directional Selection, which drives a feature in one direction.
- Stabilizing Selection, which favors intermediate traits.
- Disruptive Selection, which traits diverge in two or more directions.

Convergent Evolution

Unrelated species may evolve similar traits because they live in similar environments.

Artificial Selection

The process of selection conducted under human direction

Biological Diversity (Biodiversity)

The variety of life across all levels of biological organization:
- species
- genes
- populations
- communities

Speciation

The process of generating new species

Allopatric Speciation

Species formation due to physical separation of populations. This is the main mode of speciation.

Sympatric Speciation

Species form populations that become reproductively isolated within the same area.

Examples:

- Feed in different areas
- Mate in different seasons
- Hybridization between two species
- Mutations

Phylogenetic Trees (cladograms)

Show relationships among species, groups, and genes. Scientists can trace how certain traits evolved.

Fossil

An imprint in stone of a dead organism

Fossil Record

The cumulative body of fossils worldwide

Extinction

The disappearance of species from Earth. Species last 1 to 10 million years.

Equation to find the number of species

Speciation minus extinction

Extinction is a natural process, BUT...

...humans profoundly affect rates of extinction and biodiversity loss affects people directly.

When does extinction occur?

When the environment changes rapidly and Natural Selection cannot keep up.

Name a few more causes of Extinction

- Severe weather, climate change, changing in sea levels
- New species, small populations
- Specialized species

Endemic Species

A species only exists in a certain, specialized area.

Background Extinction Rate

Extinction usually occurs one species at a time.

Mass Extinction Events

Killed off massive numbers of species at once.

Cretaceous - Tertiary Event

Dinosaurs went extinct 65 Million years ago

End-Permian Event

75-95% of all species went extinct 250 million years ago

How are we causing the 6th mass extinction event?

- Resource depletion, population growth, development
- Destruction of natural habitats

Biosphere

The total living things on Earth and the areas they inhabit.

Community

Interacting species living in the same area

Ecosystem

Communities and the nonliving material and the forces they interact with.

Population Ecology

Investigates the dynamics of population change and the factors affecting the distribution and abundance of members of a population and why some populations increase and others decrease.

Ecosystem Ecology

Studies living and nonliving components of systems to reveal patterns and to see how nutrient and energy flows.

Habitat

the environment where an organism lives, including living and nonliving things.

Habitat Use

Each organism thrives in certain habitats, but not others.

Habitat Selection

The process by which organisms actively select habitats in which to live

Niche

An organism's use of resources. This term can also refer to the organism's functional role in a community, it's habitat use, food selection, role in energy and nutrient flow, and interactions with other individuals.

Specialists

Have narrow niches and specific needs. Extremely good at what they do, but vulnerable when conditions change.

Generalists

Species with broad niches. They use a wide array of habitats and resources and can live in many different places.

Population Size

The number of individual organisms present at a given time.

Population Density

Number of individuals in a population per unit area.
There are "low" and "high" densities

Low Densities

For large organisms, who need many resources and a large area to survive. It is more difficult to find a mate with less organisms due to lack of space which is caused my the size of the organisms.

High Densities

Easier to find mates, but there is an increase in competition and vulnerability to predation. There is also an increased transmission of diseases.

Population Distribution (dispersion)

Special arrangement of organisms:

- Random Distribution
- Uniform Distribution
- Clumped Distribution

Random Distribution

Haphazardly located individuals and there is no pattern.

Uniform Distribution

Individuals evenly spaced. This distribution includes territoriality and competition.

Clumped Distribution

Arranged according to availability of resources. This distribution is the most common in nature.

Sex Ratio

proportion of males to females

Age Distribution (structure)

the relative numbers of organisms of each age in a population. Displayed in an "Age Structure diagram" (pyramid).

Survivorship Curves

the likelihood of death varies with age

Type I: more deaths at older ages
Type II: Equal number of deaths at all ages
Type III:more deaths at younger ages

Natality

Births within the population

Mortality

Deaths within the population

Immigration

Arrival of individuals outside of the population. Adds to number of individuals

Emigration

Departure of individuals from the population. Subtracts from number of individuals.

Crude birth (death) rates

number of births (deaths) per 1000 individuals per year

Natural Rate of populations growth

(crude birth rate) - (crude death rate)

Population Growth Rate

(crude birth rate + immigration rate) - (crude death rate + emigration rate)

Exponential Growth

A populations increases by a fixed percent. Graph has a J-curve. It occurs in nature due to small population, low competition, and ideal conditions.

Limiting Factors

physical, chemical and biological attributes of the environment. They restrain population growth.

Environmental resistance

all limiting factors taken together.
- stabilizes the population size
- space, food, water, mates, shelter

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